System of control



R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLICATION FILED JULY 5. m7.

1,371,559. Patented Mar. 15, 1921,.

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WITNESSES INVENTOR d/ 0! W I Ru of [He/M71117 R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLICATION FILED JULY 5.1917.

Pat/81nd Mar. 15, 1921.

2 SHEETS-SHEET 2- round wlTNEs sl -isz /52 ATTORNEY UNITED STATES PATIENT OFFICE.

BUDOLF E. HELLM UND, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC 8c MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

SYSTEM OF CONTROL.

Patented Mar. 15, 1921.

Application filed July 5, 1917. Serial No. 178,550.

T 0 all whom it may concern:

Be it known that I, RUDOLF E. HELL,- MITND, a subject of the Emperor of Germany, and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Control, of which the following is a specification.

My invention relates to systems of control and especially to the automatic control of dynamo-electric machines under predetermined abnormal conditions.

In the prior art, various systems .have been proposed for preventing slippage and skidding of the wheels of a locomotive or other electric railway vehicle during either the accelerating or the regenerative period. some systems disclosing means for entirely interrupting the machine circuits under such abnormal conditions and other systems illustrating means for weakening the field excitation of one of the machines under such conditions of slippage or skidding.

the matter of expense and weight, for example.

The object of'my present invention, therefore, is to provide a relatively'simple and inexpensive system for eliminating slippage or skidding of vehicle wheels during either the accelerating or' the regenerative period by modifying circuit connections in such manner that occurrences of slight abnormal conditions are immediately compensated for, while, whenever the slippage or skidding conditions are pronounced or relatively long in duration, other circuit connections are also modified to eliminate the abnormal conditions.

My invention may best be understood by reference to the accompanying drawings, wherein Figure 1 is a diagrammatic view of the essential main circuits of a system of control embodying the invention; Fig. 2 is a diagrammatic view showing the complete details of construction of one of the switches that is illustrated in Fig. 1 Fig. 3 is a diagrammatic view of an auxiliary governing system for the main circuits that are illustrated in Fig.1; Fig. 4 is a sequence chart of well-known form, indicating the normal changes of circuit connections durin both acceleration and regeneration; and *ig. 5 and Fig. 6 are simplified diagrammatic views, corresponding to Fig. 1, of modified forms of my invention.

Referring to Fig. 1 of the drawings, the system shown comprises suitable supplycircuit conductors, trolley and ground; a plurality of main dynamo-electric machines respectively having commutator-type armatures A1 and A2 and field windings F1 and F2 of the series type; a plurality of translating devices or stabilizing resistors R1 and R2 that are associated with the respective main machines in a manner to be set forth; a plurality of switches LS, J, 1 to 8, inclusive, M and G for effecting various circuit connections; a polarized relay device 10; a series differential relay 11; a parallel differential relay 12; an auxiliary source of energy for the main field windings, preferably comprising a motor-generator set 13; and a plurality of main-circuit resistors R3, 17, 18 and 19 which are employed to govern the machine operation in a manner tobe set forth;

The polarized relay 10 comprises an actuating coil 25 that is traversed by the total main-machine current to electromagnetically actuate a movable contact member or disk 26, with which is operatively associated a permanent magnet 27 or its equivalent. The arrangement of parts is such that when accelerating current traverses the main machines and the actuating coil *25, a magnetic repulsion obtains between the contact disk member 26 and the permanentmagnet 27, whereby the relay assumes its upper position marked Ace, whereas,

during the flow of regenerative current preferable type of polarized relay is that embodying a small motor, but for the sake the current traversin of simplicity and clearness, I have herein illustrated a solenoid-type relay.

Theparallel differential relay 12 comprises a plurality of difierentially-related, preferably concentrically-Wound, actuating coils 28 and'29 which are respectively energized by the currents traversing the main armatures A1 and A2 during parallel connection thereof, that is, under high-speed accelerating or regenerative conditions. A contact member 30 is electromagnetioally actuated to its upper or open position whenever the currents traversing the aotuati coils 23 and 29 differ by a predeterminei amount, for the purpose of controlling certain auxiliary circuits to be described in connection with F 3. The series differential relay l1, accomplishes a similar function.v when the main armatures A1 and A2 are connected in series relation, that is, during the initial accelerating or final regenerative period. Since both main machines during series connection thereof is the same under all conditions, the parallel differential relay 12 would be ineffective to produce the desired result and, consequently, the series difierential relay 11 is provided with actuating coils 31 and 32 which are respectively connected across the main armatures A2 and A1 to actuate a contact member 33 in accordance with the differential relation of the voltages upon the main armatures. To

prevent the series differential relay 11 from governing any auxiliary, circuits during the parallel connection of the main machines, the rela may be mechanically or electrically interloc ed to prevent such undesirable operation. In the resent instance, interlocking contact mem ers J-in, -of the familiar type that is fully illustrated in Fig. 2, are

connected in circuit with each of the actuating coils 31 and 32. Since theswitch J is employed only during series connection of the main machines, as subsequently traced in detail, the employment of such interlocks serves to preclude operative action of the relay device 11, except when the machines are series related.

The motor-generator set 13 is shown as comprising an auxiliary driving or motor armature 35 whichis mechanically'coupled to a generating "or exciting armature 36 by means of a shaft 37, for example. A seriesrelated field winding 38 for the motor armature 35 and an exciting field windin '39 for the generating armature 36 are provi ed, the

complete arrangement inafter fully traced. v

The resistors 17 and 18 are connected in series relation with the respective main armatures A1 and A2 for the familiar purpose,

of circuits being-hereof reducing the voltage applied to the armatures under initial fseries and parallel accelerating conditions, for example, andarmature 36.

arness sets of switches 5 and 6, and 7 and 8 respectively, are adapted to graduallyshortcircuit the resistors 17 and 18, as determined by the auxiliary governing system of F ig.

3. The resistor 19 is employed during transitional periods of the main machines from parallel to series relation, or vice versa to prevent an undesirable current surge. 'lhe normally short-circuited resistor R3 is connected in the main circuit of both armatures- A1 and A2, and is arranged. to be actively inserted in circuit by the opening movement 7 cuit (indicated bythe solid arrows) is es'-'- 7 tablished from the supply-circuit conductor ground, through conductors 45 and 43, the

resistor R3 or its short-circuiting switch 3,.

and conductor 47 to junction-point 48,

where the circuit divides, one branch includ-' I ing stabilizing resistor R1, switch 1 in its closed position, conductor e9, main armature A1, conductor 50, resistor 17, or its associated switches5 and 6, switch M, conductor 51 and the actuating coil'28 of the parallel difierential relay 12 to a second junction:

point 52, and the other branch including.

stabilizing resistor R2, switch 2', conductor 53, switch Gr, resistor 18 or its short-circu ting switches7 and 8, conductor 54, main V Y actuating coil 29 of the parallel difierential f armature A2, conductors 55 and 56 and the relay12 to the junction-point 52, whence a common circuit is continued through conductor 57, the actuating coil 25 of the polarized relay 10, conductor 58 and, the'line switch. LS to the supply-circuit conductor trolley.

The main field winding mexciting circuit (indicated by the dotted arrows 1S established fr'omathepositive terminal of the generating armature 36 through conductors- 60 and 61 to the conductor 43 and thence to;

the junction-point e8, as already traced, where the circuitdivides, one branchit'raversing stabilizing resistor R1, switch? 1, main field winding F1 and conductor 32 to the junction-point 63, and the other branch traversing stablizing 'resistorRfZ, switch 2,

mainnfield winding F2 and conductor 6i,

to the junction-point 63, whence a common circuit is completed through conductor 65 V V generating to the negative terminal of the An auxiliary circuit is completed from the I line switch LS through conductors 58 and 66, field winding 38and the associated driving armature winding 35, exciting .field winding 39' forthe generatingiarmature 36 and conductors 61 and45 to ground. The regenerative circuit connections just recited are not of my present invention but are fully set forth and claimed in my copending application, Serial No. 44,443, filed August 9, 1915, and patented April 1, 1919, No. 1,298,706. Consequently, only a brief description of the operation thereof will be necessary to afford a thorough comprehension of the present invention.

As indicated by the solid and dotted arrows, respectively representing regenerative and exciting current, such currents traverse the stabilizing resistor R1, for example, in the same direction during the regeneratlve period. Hence, upon an incipient increase of regenerated current, the correspondingly augmented voltage dro across the resistor R1 immediately and in erently reduces the voltage available for delivery to the main field winding F1 from the generating armature 36, thus causing the current traversing the main armature A1 to subside to a normal value. On the other hand, when an incipient decrease of current traversing the mainarmature A1 takes place, the converse action results by reason of the peculiar connection of the stabilizing resistor R1, and the main-armature current is raised to the desired average value. Consequently, a substantially constant regenerated current 1s inherently maintained, irrespective of supplycircuit voltage fluctuations.

A corresponding inherent stabilizing action' obtains during accelerating operation of the main machines also. In this case, the main-armature current traverses the resistor R1 in the opposite direction to the exciting current from the generating armature 36. Consequently, upon an increase of current in the main armature, the difl'erential relation of currents efiects a decreased voltage drop in the resistor R1 and, therefore, an increased energization of the main field winding Fl. In this wayfgthe counterelectromotive force of the main armature Al is increased to cause a corresponding reduction of the accelerating current in the armature. The converse action takes place in the event of an incipient decrease of accelerating current. Consequently, under acceleratin conditions also, the stabilizing resistors 1 and R2 serve to maintain a sub stantially constant main-machine current, irrespective of supply-circuit voltage fluctuations.

Reference may now be had to Fig. 3, wherein the auxiliary governing system shown comprises the.actuating coils of the various switches and the auxiliary contact members of the various relay devices that are shown in Fig. 1, together with a master controller MC that is adapted to occupy a plurality of operative positions a to g, corresponding to acceleratlon and a to d, correspondlng to regeneration; an auxiliary sourceof energy, such as a battery B; and

a plurality of time-element relay devices and 71 for effecting certain automatic control functions to be set forth.

The relay devices 70 and 71 are identical in form and each comprises an actuating coil 72 for electromagnetically operatin a movable contact member or bar 73 t at slides along a pairof stationary contact members 74, in opposition to the action of a dash-pot 75 when traveling downwardly. Thus, a predetermined time interval ensues after the deenergization of the actuating coil 72 before circuit is broken between the stationary and movable contact members 74 and 73, respectively.

,Assuming that it is desired to effect ac celeration of the main machines, the master controller MC may be moved to its initial operative position a, to close the switches indicated in line a of the sequence chart,

Fig. 4, whereby acircuit is established from the positive terminal ofthe battery B through conductor 80, controlfingers 81 and 82 which are bridged by contact segment 83 of the master controller, conductor 84, the parallel-related actuating coils of the switches LS, 1 and 2 and conductor 85 to the negative battery terminal.

A further circuit is completed from the contact segment 83 through control finger 86, conductor 87 and the actuatingcoil of the switch 'J to the negative battery conductor 85. The main circuit is thus established from the trolley through line switch LS, actuating coil '25 of the polarized relay tinued from control finger 88 through conductor 90, the actuating coil of the switch 3 to a junction-point 91, conductor 115, stationary and movable contact members 74 and 73, respectively, of the time-element re- .lay 71, whichhas been closed in a manner about to be described, conductor 116, mm trol fingers 117 and 118 which are bridged by contact segment 119 of the master controller, and conductor 120 to the negative battery conductor'85.

' The closureof the time-element relay 71 to effect the establishment of the circuit just recited, is accomplished, upon the closure.

of the switch 4, by the establishment of a circuit from the positively-energized control finger 82, through conductor 125, control fingers 126 and 127 which are bridged bycontactsegment1280f the master controller-fin ositions a and b, conductors 129 and 135, t e actuating coil 72 of the timeelement relay71, and conductor 136 to the negative battery conductor 85.

In positions ofthe master controller beyond b, the. movable contact member 137 of 'the switch a or the parallel-connected movable contact member 138 of the switch 7, to-

control finger 83 through conductor 92, actu- 1' "set forth, conductors 94 and 95,. contact disk; T '26; of the polarized relay 10 in' 'its upper ating coil of the switch a, conductor 93, stationary and movable contact members 7 i and 7 3, respectively, of the time-element relay 70, which has been closed 111' a manner tobe position'corresponding to acceleration, the

tact segment 128 of the master. controller, conductors 129 and 130, movable contact movablecontact members30 and 33 of the difiere'ntial relays 12 and 1-1, respectively, In their lower or normal positions, and conductor 96130 the negative conductor 85.'

Ilieclosureof the time-element relay 70' sefiected to permit the completion ofthe circuit just described, upon the closureof the switch 3, by the establishment of a cir- 'cuit from the ositively-energized control finger 82 throng conductor. 125 control fingers126 and 127 which are bridged by conmember131 of theswitch 3 in its upper or closed sltion, conductor '132, the actuat ing co -72 of the relay 70 and conductorv I 133 to the negative conductor 85. V

and :13 are shortscireuite'd by the switches 3 and 4, res ectiyely, to efiect a certain de- 4-5 gree of acce eration of the main machines.

w trol 0 1 which point a circuit is. continued.

At this time, therefore the resistors R ingosition c of the master controller, connger 97. engages the contact se out I through conductor 98, the parallel-related actuating coil of the switchesh' and 7' to conductor 93 and thence-'throu hthe coip eratingcontaet members of t e'relay dc vices 70,10, Portiohsof 12,'-' and 11'; as already. traced. the resistors 17 and 18ers thus short-'circuited to further accelerate the main motors. i

v e n the master controller is actuated to ts posit on (2, the contact segment 83 completes a circuit through control finger 99,

conductor 100 and the parallel-related actu atin coils of the switches t end 8- to the con uctor 93, thereby exiciudin from cireuit the remaining sections of t e resistors 17 and 18. positionse and f of the master eontarmac troller, the well-known bridging transition ofythe' main machines from series to parallel relation is efi'ected by first opening the switches '3 to 8, inclusive, by means of suitable configuration of the master-controller contact segment 83 and the closure of the parallel-connectin switch M byenergizin'g its actuatin 0011 through control nge'r 101 and con uctor 102. A further "'circuitis then established from the contact segment 83 through control finger 108, conductor 109. and the actuating coil of the switch G to the negative battery conductor, whereupon the switch J is permitted to open. Under such conditions, the main armatures A and A are connected in parallel relation in accordance with the previousl -described circuits of Fig. 1.

T e various active resistors may then be short-circuited in any desired number of steps, as indicated in positions f and g of the sequence chart, Fig. 4.

Assuming that the voltage relation of the momentumdriven dynamoi-elebtric machines and of the supply circuit is suitable for such action, the master controller MC maybe moved to its initially operative position a, whereby the switc es LS, 1, 2, 5, 6, 7, 8, M and G are closed, as indicated in line a of the sequence chart. v

"In position h the switch 3 is also closed, after stable regenerative conditions. obtain, to permit full tion of the mac ines.

. The various switch-coil circuits are establishedas follows: from the actuating c011 of the switch 3 through 'unction-point 9 1, conductor 121, the movab e contact member 26v of the polarized relay 10 in its lo'wer orregenerative position, and thence throu h the contact members 30 and 33 of the differential relays12 and 11, respectively, in

their lower or normal positions, to the he ap tive "battery terminal, as previously traced. The circuit ofth'e actuating coils for the aralle regenerative operaswitches 4 to .8, inclusive, is estabiished as precluded, since only that relay is operative which itis desired to utilizeduring the accelerating'or regenerative period. r

Whenspeed conditions are such that a transition'of the machines from parallelto series relation isfeasible, the master con 'troller may be moved to position 0' to open the resistor shor -circuiting switches 5,- 6,

contact segments, false relay operation is 7 and 8, close the transition "switch J to include the resistor 19 in circuit and open the parallel-connecting switch G. Upon actuation of the master controller to position 01', the other parallel-connecting switch Mis opened and the resistor shortcircuiting switches 5 to 8, inclusive, may then be closed in any desired sequence. In this way, by the use of the transition resistor 19, an undesirable current surge during the changeover from parallel to series relation of the main machine is prevented.

Inasmuch as suitable regulation of the regenerative system to compensate for the gradual decrease of vehicle speed is familiar in the art and since the particular type of regulation is immaterial to the present invention, I have not deemed it necessary to illustrate or describe any such compensating system. It will be understood, however, that the excitation of the main field windingls F1 and F2 is gradually increased as the ve icle speed decreases to maintain a steady regenerative current.

The operation of the system under the previously-mentioned abnormal conditions of wheel slippage or skidding will now be set forth: assuming that the machines are operating during series acceleration, for

example, so that the series differential relay coil 72 of the time-element relay 71.

11 is operatively connected in circuit and the polarized relay l0 occupies its up or position, in case either main' armature 1 or A2 rapidly rotates by reason of slippage of the corresponding vehicle wheels, the unbalanced relation of voltages in the actuating coils 31 and 32 of the series dilferential relay 11 immediately causes the relay to lift to its upper or open-circuit position. Consequently, the previously-traced circuit of the actuating coils of the switches 4 to 8, inclusive is interrupted and theresistors 17,- 18 and 19 are re-inserted in the'machine circuits to counteract the abnormal unbalanced voltage conditions of the main machines and thereby tend to eliminate the slippage conditions. 7

- Under slightly abnormal conditions of the class in uestion, that is, when arelatively slight di erence of armature'speeds obtains, it is undesirable to weaken the main-machine field excitation and, consequently, the switch 3, which short-circuits the common field-circuit resistor R3, is maintainedclosed.

However, if slippage conditions persist after the o ening movement of the switches 4 to 8, inc usive, then the switch 3 may be opened to weaken the main-field-winding excltation and thus insure the elimination of the abnormal conditions. .Such delayed actuation of the switch 3 is efi'ected by reason of the inclusion of the movable con-.

tact member 137 or 138 ofthe switches 4 and 7, respectively, in circuit with the actuactjing onsequently, upon the opening movement of plishes the same function by interrupting the above-mentioned energizing circuit of the resistor short-circuiting switch coils when the machines are connected in parallel relation during the latter part of the accelerating period. Under such conditions, the series differential relay 11 is inoperative by reason of the exclusion of the electrical interlocks J -in from the circuits of the actuating coils thereof, as previously explained.

On the contrar during regenerative operation, it is desirable first to Weaken the main-field-winding excitation, thus resulting in a material reduction of the regenerated current as well as the corresponding torque until the skidding conditions are eliminated. If, however, normal conditions 1 ding conditions in any main armature, as

evidenced by a marked difference in'the currents traversing the actuating coils 28 and 29 of the parallel diiferential relay 12,causesthe relay 12 to lift to its upper or circuitopening position, whereby the previously traced energizing circuit of the actuating coil for the switch 3 through the cooperating contact members of the polarized relay 10 is interrupted to produce the previouslydescribed partial or complete elimination of the abnormal skidding conditions.

If such abnormal conditions persist, the time-element relay 70, which was deenergized b the opening movement of the switch 3, gra ually drops to its open-circuit tion 'in accordance with the action 0 the dash-pot 75, and after a predetermined timeinterval, the energizing clrcuit of the actuatswitches 4 to 8, inclusive, is broken.

It will thus be seen that I have provided an automatically operative system for eliminating abnormal slippage or skidding conditions in an electrical vehicle during both accelerating and regenerative operation with the main machines in either series or parallel osi- .ing coils for the resistor short-circuitingl relation. During acceleration, the mainarmature-circuit resistance is first increased to eliminate the abnormal conditions and if such action is insuflicient, the main-machine field windings are then simultaneously weakened by the short-circuiting of a single resistonwhile, during regeneration, the converse action is efiected.

Referring to Fig. 5, the system illustrates an arrangement correspondingto the previously-described regulating systems to be employed in the case of three series-connected,

.' main machines which are respectively provided with armatures A1, A2 and A3 and field windings F1, F2 and F3. The resistor R and the generating armature 36 are connected in circuit in a manner similar to that already set forth. The system further comprises a plurality of voltage differential relay devices 151, and an exciting circuit resistor 152, with short-circuiting switch 153,

. that respectively correspond to the resistor B3 and the switch 3 of Fig. 1. a

Each voltage differential relay 151 comrises an actuating coil 155, all of the coils eing connected in series relation across the three main armatures A1, A2 and A3. Differentially-related coils 156 are energized from therespective main armatures and the normal resultant action of thecoils 155 and v 156 is to maintain the movable contact member 157 in its lower or inactive position.

However, as soon as any one of thearmatures supplies or receives a voltage difiering by a predetermined amount from the average' volta of the machines, in this case one-third'o the simultaneous total machine voltage, the corresponding relay device will lift to govern the various machine circuits prefera ly in a manner similar to that already set forth in Fig. 3.

In Fig. 6, a difi'erential current relay scheme for suitably governing three parallelrelated, main armatures, in accordance with 45 illustrated A relay device 160 is provided, n COHDGCtlOD with each mam-armature the principles of my present invention is and A3, and comprises one actuating coil 161 which is connected in series relation w1th the corresponding actuating coils of the-other relays'across a main circuit resistor or shunt 162 that-carries the total mainer provided with' a difiere entially-related actuating coil 163 which is balanced in theiraction. and maintain the position. ."l-Iowever, when the currenttraversing any one or the main armatures varies materially I contact members 164 in theillustrated lower windings, of auxiliary means for arness from theaverage current of the machines, in this case one-third of the simultaneous total machine current, by reason of slippage vention comprises the actuation of railsanding devices whenever any one of the differential relays is actuated to an opencircuit or unbalanced position. Such an auxiliary system is fully set forth and claimed in my copending application, Serial No. 70,437, filed January 5, 1916. Inasmuch as theconnection between the present invention and the use of such sanding devices will be obvious to those skilled in the art, no illustration or further description thereof is deemed necessary in the present application.

do not wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be efi'ected without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In a system of control, the combina tion with a plurality of dynamo-electric machine's severally havin armatures and field windings, of a norma y inactive translating device connected in common circuit relation with all of said field windings, and

means dependent upon a predetermined difference in the machine speeds for rendering said translating device ,active.

2. In a system of control the combination with aplurality of dynamo-electric machines severally'having armatures and field windings, of a normally short-circuited resistor-connected in common series relation with all of said armatures, a single auxiliary source of energy for exciting all of said field windings through said resistor, and relay means electrically dependent upon a predetermined diiference in the machine said resistor. v

3. In a system of control, the combination with; a plurality of dynamo-electric machines severally having armatures and field exciting said field windin s, and means dependent upon a predetermmed difi'erence of machine speeds for removing the short-circuit from speeds for simultaneously reducing the excitation of all said field windings.

4. In a system of control, thecombination termined relatively. sli

with a plurality of dynamo-electric max chines severally having armatures and field windings, of means. dependent upon slippage or skidding conditions for dissimilarly modifying machine-circuit connections during accelerating and regenerative periods.

6. In a system of control, the combination with a plurality of dynamo-electric machines severally having armatures and field windings, of means dependent upon a predetermined diiierence of machine speeds for reducing the armature voltage during accelerating periods and for decreasing the field-winding excitation during regenerative. eriods. 7. n a system of control, the combination with a ,plurality of dynamo-electric machines severally having armatures and field windings, of means dependent upon a predetermined difference of machine speeds for first reducing the, armature voltage and subsequently decreasing the field-wlnding excitation during accelerating periods and for effecting a converse regulation during regenerative periods.

8. In a system of control, the combination with a pluralit of dynamo-electric m'achines severally aving arinatures and field windings, of means dependent upon a predetermined difierence of machine speeds for effecting a series of regulating operations in a certain'order during accelerating period and in the reversed order during regenerat1ve eriods.

9. n a system of control, the combination v with a plurality of dynamo-electric machines 45 several y having armatures and field windings, of' means dependent upon a predetermined difference of machine speeds for immediately effecting the one or the other of two machine-circuit modifications during accelerating and regenerative periods, respectively, and means for effecting the re maining modification in either case after a predetermined time interval.

10. In a system of control, the combina-, -t1on with a plurality of dynamo-electric machines severally having armatures and field windings, ofimeans de endent upon predet diflerences of machine speeds for imme iately modifying. certain machine-circuit connections, and means dependent upon relatively reat differences of machine speeds formo fying different machine-circuit connections.

11. In a system of control, the combination with ,a plurality of dynamo-electric machines severally having armatures and field windings, oi means dependent upon predetermined relatively sli ht differences of machine speeds for imme iately modifying certain machine-circuit connectionsand means dependent upon the persistence of such difi'erences for modifying difierent machine-circuit connections during the accelerating period, and means for effecting the converse action during the regenerative period.

12. In a system of control, the combination with a plurality of dynamo-electric machines severally having armatures and field windings, of means dependent upon predetermined relatively slight diiierences of machine speeds for immediately reducing the armature voltage and means dependent upon the persistence of such differences for decreasing the field-winding excitation during the accelerating period, and means for effecting the converse action during the regenerative period.

13. In a system of control, the combination with a plurality of, dynamo-electric machines severall having armatures and field windings, 0 an auxiliary source of energy for said field windings, relay means dependent upon predetermined relatively slight differences of machine speeds for immediately reducing the armature voltage and time-element means dependent upon the persistence of such differences-for a predetermined time interval for decreasing the field-winding-excitation during the acoelerating period, and a similar set of means for effecting the converse action during the regenerative period.

14. In a system of .control,-the combination with a plurality of dynamo-electric machines severally having armatures and field windings, of means or effecting seriesparallel operation of said machines, relay means dependent upon predetermined differences of machine speed as indicated by relative voltage conditlons in said machines for modifying certain circuit connections during'series relationv of the-machines, and relay means dependent upon such speed differences as. indicated by relative current conditions in said machines for modifyin such connections during parallel relation 0 the machines.

15. In a system of control, the combination with a plurality of dynamo-electr1c machines severally having armatures and field windings, of means for effecting seriesparallel. operation of said machines, rela means dependent upon predetermined di ferences of machine speed as indicated by relative voltage conditions in said machines for modifying certain circuit connections during series relation of the machines, re lay means dependent-u on such speed differences as indicated 8 eratingoperation and parallel-series rethe machines, and inter the first-mentioned relay meansconditions insaid machines for modifying such' connections during 'arallel relation of ocking means for rendering inoperative during such parallel relation.

16. .In a system of control, the combination with a .plurality of dynamo-electric machines severally having armatures and field windings, of a polarized relay device for assuming difierent operative positions in accordance with the accelerating or regenerative operation of said machines, and relay means dependent upon a predetermined difference of machine speeds and acting in conjunction with said olarized relay device for dissimilarly modi ying machine-circuit connections during accelerating and regenerative periods.

17, In a system of control, the combination with a plurality of dynamo-electric machines severally having armatures andfield windings, of a polarized relay device for assuming in accordance generative operation ofsaid machines, relay means dependent upon predetermined relatively slight difierences .of machine speeds and acting in conjunction with said polarized relay ing certain machine-circuit connections and means dependent upon the persistence of such-,diflerences for a certain time interval generative operation of said machines,

means .for efiecting series-parallel accel generative operation of said machines, rela means dependent upon predetermined di peed as indicated by ferences of machine s relativevoltage condit ons 1n said machines ative current the combination with a mo-electric machines severally having armachanges of field-circuit diflerent operative positions with the accelerating or re-' device for immediately modifytion with a system of control, the combina- -'t1on with subscribed enses and acting in' con'un ction with said polar-- ized relay devlce or modifying certain circult connections during seriesrelation' of.

the machines,

and upon the position of said polarized rerelay means dependent upon such speed differences as indicated by rel-- conditions in said machines laydevice for modifying such connections during parallel relation of the and interlocking means for rendering the. first -mentioned relay means durin such parallel relation.'

tures and field windings, energized to effect certain compensating excitation of all machines while maintaining the generalmachine-circuit arrangements intact when certain electrical conditions of any one -machine differ by a predetermined amount Y from the corresponding average condition.

. 20. In a system of regenerative control,

the combination with a plurality of seriesrelated dynamo-electric machines severally having armatures and field windings, of

relay means energized to efi'ect certain re-' storative changes of field-circuit excitation of all machines while 'maintaming the general machine-circuit arrangements .intact when the volta e of any one machinev difiers by a predetermined amount from the simultaneous average voltage of the machines.

7 21. In a system of control, the combinaa plurality of parallel related dynamo-electric machines severally having armatures and field windings, of relay means energized to eflect certain changes of machine-circuit connections oi allmachines while maintaining. themin parallel machines,

n a system of regenerative control,

plurality of dynainoperative relation when'the current traversing any I one machine differs by a predetermined amount fromthe simultaneous average current of the machines.

In testimony whereof, I *havefhereunto enoir HELL Q my name this 28thday of June,

6 5 of relay means 

